Methods for three-dimensional detection of objects are needed for different purposes, including the identification and authentication of persons. Thus for example projecting a two-dimensional color pattern made of colored pattern elements and using a camera to record the color pattern projected onto the object to be detected is known from DE 199 63 333 A1. As a result of the spatial properties of the surface of the object to be detected the color patterns in the image recorded by the camera are shifted in relation to the original arrangement, so that for a known position of the projector and the camera, the three-dimensional data of an object point on the surface of the object to be detected can be calculated.
The known method is however not suitable for colored scenes. Instead, with the known method, it is necessary to record a reference image with evenly white object illumination. This reference image allows the projected colors in the sample image to be determined. Since with the known method at least two images need to be recorded, it is limited as to its suitability for moving objects or objects which change their shape. Thus this known method has only restricted suitability for detecting a hand or a face.
Projection of a black and white two-dimensional pattern with additional encoding into the object to be detected is known from the publication by P. Vuylsteke and A. Oosterlinck, “Range Image Acquisition with a Single Binary-Encoded Light Pattern”, IEEE Transactions on Pattern Analysis and Machine Intelligence, Volume 12, No. 2, February 1990. This attempts to determine the angle of projection for each point of the camera image from the image environment of the point. In particular it attempts to calculate the angle of projection of the relevant point from the distortions of the projected pattern arising from the spatial orientation of the object surface as viewed by the camera. However this only succeeds well for objects with a constantly moving surface. If however indentations are present on the object to be detected, the coding pattern elements of the pixel environment are disturbed, which results in non-determinable or incorrect projector angles and leads as a result to incorrect three-dimensional object coordinates.